The episode starts by showing planet Earth from space, and then zooming into a Christmas decoration in Rose Tyler's house. Rose's mother Jackie Tyler spies a Christmas present meant for Rose, and Mickey Smith is seen working in a garage, and both Mickey and Rose's mother hear the TARDIS arriving, but don't know where it is coming from. They then see the TARDIS come in, crashing around, finally stopping.

TARDIS entering from the Time Vortex

The newly regenerated doctor comes out, says Merry Christmas to Mickey and Jackie, and then collapses. Mickey asks who they are and where the Doctor is, and Rose tells them that he is the doctor, to which Jackie replies: "Doctor Who"? The Doctor is then moved to a bed, and Rose listens to his hearts, to make sure they are beating. She announces that they are both beating, and Jackie thinks that she is joking. The Doctor sighs in his sleep and releases regenerative energy that travels into space.

Jackie asks how the Doctor can change his face, and Rose says she doesn't know, and then breaks down, as she thought she knew the doctor. Rose notices Harriet Jones is on the television, and finds out she is the current Prime Minister. The news also mentions a probe that is going to show images of martian lands.

Mickey and Rose talk about stories of the TARDIS whilst walking down the street, and they stop in front of a band, so Mickey can tell Rose to stop talking about life or death and about the doctor. Rose looks at the band, and notices one was looking at her, she then sees them walking around. They stop playing and hold the instruments under their arms, then start firing at Rose and Mickey. Rose dictates that they are after them. One of the Santa masks falls off, and Rose jumps into a taxi with Mickey. Rose proclaims that they are after The Doctor, who is still breathing out regenerative energy.

Rose storms into her house, and Rose asks about a new tree, and who put it there, the tree lights up, and then starts spinning, and moving towards them breaking things in its path. Mickey tries to stop it using a chair.

Mickey Versus a Spinning Tree

He fails, and they all flee into the room which the Doctor is unconscious in. Rose grabs the sonic screwdriver out of the Doctor's pocket, sticks it into his hand, and whispers "help me" into the doctors ear. He jumps up in response, uses his sonic screwdriver to blow up the tree. The Doctor points out that the tree was remote controlled, and that the only question was as to who was controlling it. They go outside and run into three Santas which the Doctor identifies as pilot fish, and they are after him for his regeneration energy. The Doctor says he needs something, but Jackie talks too much for him to say. He goes to tell Rose that the pilot fish mean that something is coming, and finds an apple in his pocket, which stumps him. Rose says that the Doctor has gotten worse, and that he has only one heart beating rather than the usual two.

The news states they have received contact from the satellite, and pictures from Mars is going to received soon. Mickey searches the internet for pilot fish, and finds that they are fish which in nature swim closer to bigger creatures. He realizes that means there is something bigger coming. Then the news displays an alien face, and all news channels begin to broadcast the footage. UNIT are seen escorting the man who was in charge of the satellite into a room full of people, and he sees the prime minister, and she tells him they are calling this a hoax. They are told that the broadcast didn't come from the surface of Mars, but from above the planet. This meant that it was caught in a ship, and they registered that the ship is moving towards Earth at a fast pace. Mickey logs into UNIT's computer, and they see a broadcast of the aliens speaking to the people of Earth. Rose cannot understand what the aliens are saying, and she concludes that the Doctor must be part of the TARDIS and he is broken so it isn't translating anymore. The news of it being a hoax is being shown on the television. Harriet Jones asks if any information of The Doctor is stated, and when there isn't she asks about Torchwood. The man comes in and tells her they have figured out a partial translation, stating that they are the Sycorax, and they come to take Earth. Rose proclaims the real Doctor would wake up and save them, and he wouldn't just stay there as the current Doctor was. Back in UNIT HQ, a message stating that Earth is a peaceful planet has been sent to the Sycorax, to which they reply.

Sycorax reply

They say that they don't know what the reply meant, but then people all from all over start glowing the same colour as the hand of the Sycorax, and all the people start walking in the same direction, all heading towards higher ground. All of the affected people step up to the edge of the roof, and stop. The message is thought to be translated as "surrender or die". They make a link that all of the people who are chosen have the blood group A+, as a vial of A+ blood was on the satellite. Harriet Jones goes on television and makes a plea to the Doctor, saying that the situation is desperate. Rose walks off and begins crying, saying that the Doctor is gone.

A sonic wave breaks every aspect of glass, caused by the space craft which had broken into the atmosphere.

The space craft is seen to slowly move over Britain, and come to a stop over Central London. Rose says they are going to carry the Doctor to the TARDIS and hide, saying it is the safest place on Earth. At this time, the aliens ask for the Leader of the planet to step forward and come aboard the space craft. Harriet Jones is then teleported aboard the craft, where the alien removes his helmet and says that he will finish the final curse, and make the people jump. The Sycorax kills two men who attempt to reason with him, and then states that if they surrender one half will be sold into slavery, otherwise one third will die. Jackie offers a cup of tea out, and Rose jokes the it's her "solution to everything". Mickey and Rose mess with the TARDIS screen and the Sycorax pick up the signal, proceeding to take the TARDIS onboard their ship. Rose goes outside to find her mother not knowing that the TARDIS has been moved and is thus captured by the aliens. Mickey hears her screaming and runs out after her. She tells him to close the door, which he proceeds to do. A flask of tea is knocked over and heats up, producing steam. The Doctor breathes in the steam, and releases another puff of regeneration power. The aliens say that Rose with the clever blue box speaks for the planet. Rose attempts to tell the aliens to leave the planet, using all the different aliens she knows as different laws, and the Sycorax laugh at her and say she is funny. The alien says that if Rose is the best champion they have then the world will be used as slaves, at which point the people present notice that they are being translated. Which meant that the Doctor was awake.

The Doctor comes out and tells the Sycorax they can wait, and asks Rose if he is Ginger. He starts to tell Rose off and then stops and points out that he is rude. Harriet says she doesn't know who he is, to which he responds that he is the Doctor. The Sycorax leader asks who he is, and demands to know who he is, and the Doctor mocks him and says he doesn't know. The doctor spots a button, which he then presses. This disconnects everyone from the Sycorax. The Doctor explains that blood control is just like hypnosis, you can't use it to kill. The Sycorax says he can bring the whole armada to take the planet. The Doctor then challenges the Sycorax, proceeding to comment in the Sycorax's native language. The Doctor sword-fights with the Sycorax leader, running out onto the top of the space craft, still fighting. The Doctor runs into the Sycorax, who then chops off the Doctor's hand which falls with his sword to the Earth below.

The doctors handing falling to Earth

The Sycorax turns around and shouts, the Doctor stands up and as he is within the first 15 hours of regeration he grows his hand back. The Sycorax calls it witchcraft. The Doctor wins, and says he will spare the Sycorax's life as long as he swears on the blood of his species to leave Earth alone.

Successful, the Doctor then walks away, finds a satsuma in his pocket, and talks about finding them at the end of Christmas at the bottom of your stocking. The Sycorax gets up and runs at the Doctor. He throws the satsuma at a button and the Sycorax falls from the ledge that vanishes beneath him. The Doctor then walks back inside, and he banishes the people from coming and states that the planet Earth is defended. Harriet asks if there are many more aliens out there, to which the Doctor states there are, and that Earth is getting noticed. They all then hug the Doctor.

Harriet Jones recieves a message from Torchwood saying they are ready, and she tells them to fire. They all look at the sky to see five shocks gather and fire at the space craft, which is then destroyed. The Doctor looks at Harriet, and calls it was murder. She calls it defense. The Doctor, now furious with her stupidity, states he could bring down the whole Government with six words, he then walks over to Harriet's assistant. "Don't you think she looks tired" he states, then walks away.

The Doctor is then seen looking through clothes, while Mickey cuts up a turkey. The Doctor finds his new signature suit and jacket, and checks himself out in the mirror.

Wardrobe within the TARDIS

The Doctor then goes and spends Christmas dinner with Rose and her family. Harriet Jones appears on television, and they say she is unfit for being Prime Minister. They receive a phone call and are told to look outside. They go outside and ash is falling from the sky like snow- the remnants of the Sycorax ship. Rose and the Doctor talk about leaving, and that they both thought the other didn't want them around. Jackie voices her opinion of them being mad. The Doctor says there is a lot to see, and it is going to be fantastic.